1. Field of the Invention:
This invention relates in general to improvements in rock bit assembly, and in particular to methods for assembling and holding rock bit sections in preparation for welding.
2. Description of the Prior Art:
A common prior art method of assembling rock bit sections in preparation for welding used dowel holes and dowels positioned between the abutting faces of the sections. This technique assured accurate vertical and radial alignment of the sections. If all parts of the pre-assembled rock bit were within dimensional tolerances, the bit diameter would be within tolerance after clamping and welding.
If rock bits were assembled in the above manner and failed to be within bit diameter tolerance, corrective measures were necessitated unless the bit was to be scrapped. One corrective measure involved removal of the dowels, scissoring the section faces relative to one another, then clamping the sections and welding them. U.S. Pat. No. 3,907,191 issued to Dresser Industries, Inc. This patent discloses the use of the non-dowel and scissoring technique for reaching acceptable bit gage diameter. This technique has the disadvantage of allowing loss of dimensional integrity. A rock bit must have dimensional integrity or else its performance may be severely restricted. Unequal loading of the sections and associated cutters results from inaccurate vertical alignment. Excessive scissoring of the sections causes the centerlines of the cutters to become aligned in a manner outside the original design parameter. Such variations lead to unpredictable performance and are to be avoided to achieve the highest quality and consistent performance.